This invention relates to the treatment of water containing dissolved oxygen to remove or scavenge the dissolved oxygen and thereby prevent or retard the corrosion of metal contacted by the water.
In oil field practice, corrosion of pipelines, metal tubular members such as casing and tubing installed in wells extending into the earth, boilers and other parts of water distribution systems by oxygen dissolved in water has long been a problem recognized in the art. Techniques of protecting metal from corrosion due to oxygen in water involving the removal of oxygen from the water are discussed by R. F. Weeter in a paper presented at an AIChE Permian Basin Technical Symposium presented at Odessa, Tex., Mar. 25-26, 1968. One method discussed by Weeter of scavenging oxygen from water involves the use of sodium sulfite and a catalyst of divalent metallic ion (usually cobalt). The reaction is Na.sub.2 SO.sub.3 +1/2O.sub.2 .fwdarw.Na.sub.2 SO.sub.4. This reaction requires eight pounds of sodium sulfite for each pound of oxygen removed plus an additional 5 to 10 parts per million to drive the reaction to completion. Another method discussed by Weeter of scavenging oxyen from water concerns injecting sulfur dioxide into the water. The reaction is SO.sub.2 +H.sub.2 O+1/2O.sub.2 +H.sub.2 SO.sub.4 . This reaction requires four pounds of sulfur dioxide for each pound of oxygen removed and approximately four parts per million additional to drive the reaction to completion.
In U.S. Pat. No. 3,618,667 to Earl S. Snavely, Jr., there is described a method of treating water which contains hydrogen sulfide and oxygen dissolved therein to retard the corrosion of metal in contact with the water by adding a transition metal to the water to catalyze the reaction between the hydrogen sulfide and oxygen and thereby remove the oxygen from the water. In U.S. Pat. No. 1,531,993 to Frank N. Speller, there is described a technique of treating water for use in boilers and the like to absorb free oxygen therefrom by adding a compound that is composed of sodium silicate and sodium sulfite. In U.S. Pat. No. 2,318,663 to Paul G. Bird et al, there is described a method of treating boiler water to prevent caustic embrittlement or intergranular attack of steel boiler plates by adding to the boiler water a combination of chemicals consisting of sodium sulfite or its equivalent and a sulfonated organic substance of suitable colloidal character such as sodium lignin sulfonate that has the property of preventing or retarding oxidation of the sodium sulfite. In U.S. Pat. No. 2,154,996 to Francis G. Rawling, there is described a method of manufacturing paper by treating broke derived from paper containing calcium sulfite as a filler or a coating substance wherein a suitable antioxidant is added to the broke to prevent the conversion of the calcium sulfite to sulfate. Sulfites, such as sodium and barium sulfite, and thiosulfates, such as sodium or potassium thiosulfate, were found to be satisfactory. Glucose, sugar, and tin salts, such as stannous chloride, were also noted as antioxidants.